共查询到20条相似文献，搜索用时 578 毫秒
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大豆是天津市南部大港区王庄镇主要作物品种。２００１年夏播面积占总播种面积一半以上。草害严重威胁着大豆的生长，制约产量的提高。经过田间调查，夏播大豆田杂草以一年生禾本科杂草为主要群落，占田间杂草数量的６０％～７０％，其主要种类为马唐、狗尾草、稗草等；阔叶杂草占杂草总数量的２０％～２５％，其主要种类有反枝苋、马齿苋等；其他杂草占２％～１０％。在大豆出苗后，杂草出土数量占９５％以上，草龄三至五叶期，可用５％精喹禾灵乳油（商品名称闲锄，下称）２０ml／６６７m２或５％精禾草克乳油５０～８０ml／６６７m２、１… 相似文献
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[目的]空心莲子草是一种世界范围的恶性入侵杂草,其贮藏根的形成在其入侵中具有重要作用,对其不定根的发生及其膨大情况进行研究有助于人们有针对性的进行防控.[方法]利用组织培养体系,对空心莲子草匍匐茎段进行无菌培养,培养条件主要考虑培养基凝固剂的类型、外植体是否带节、外植体节下茎段长度、外植体扦插方式和扦插深度.[结果]空心莲子草茎段比较理想的组培条件为:带1节长度为4 cm的去叶空心莲子草茎段,使用体积分数75％酒精浸泡1 min,0.1％升汞浸泡6 min消毒,在MS培养基中连续继代培养,采用第3代无菌苗的茎段作为外植体,在含有普通琼脂的MS培养基(钾离子浓度降至标准培养基60％)条件下,节下部长度为1.5 cm带节外植体正向扦插深度为1.4 cm的时候,可以获得生长良好的空心莲子草植株.实验发现外植体的下部截口上方的茎段能够不经过愈伤组织诱导直接生长出不定根,即出现节间生根现象.外植体培养70 d时,发现有部分不定根出现膨大趋势.继续培养80 d后,笔者观察到空心莲子草不定根出现明显膨大.[结论]研究成功构建了空心莲子草茎段不定根膨大的组织培养体系,为进一步在组培条件下开展空心莲子草贮藏根的形成机理研究提供依据. 相似文献
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新疆苔藓植物的染色体观察 总被引：1，自引：0，他引：1
报道了进行苔藓植物细胞学研究的方法和５种新疆产的苔藓配子体生长点细胞有丝分裂中期的染色体数：（１）银藓Ａｎｏｍｏｂｒｙｕｍ ｆｉｌｉｆｏｒｍｅ（Ｄｉｃｋｓ．）Ｈｕｎｓｎ．,ｎ＝１０;（２）细叶真角藓Ｂｒｙｕｍ ｃａｐｉｌｌａｒｅ Ｌ．ｅｘＨｅｄｗ．,ｎ＝１０;（３）柔叶真藓Ｂｒｙｕｍ ｃｅｌｌｕｌａｒｅ Ｈｏｏｋ．,ｎ＝１０;（４）牛角藓Ｃｒａｔｏｍｅｕｒｏｎ ｆｉｌｉｃｉｎｕｍ（Ｈｅｄｗ．）Ｓ 相似文献
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少花蒺藜草是我国重要外来入侵植物之一。研究了环境因子对少花蒺藜草种子萌发和出苗的影响。研究结果表明,光照会促进少花蒺藜草种子休眠,少花蒺藜草种子萌发温度范围为15～40℃,最适萌发温度为25℃,萌发的临界温度在10～15℃;临界水势在－12～－10 MPa,水势在－8～－4 MPa的环境适宜少花蒺藜草生长。少花蒺藜草出苗临界土壤含水量在1．0％～2．5％,生长临界含水量在2．5％～5．0％;少花蒺藜草在pH值为2～12的条件下均可萌发生长,但pH值为12的条件更适合生长;少花蒺藜草种子在沙土中0～15 cm深度均可出苗,1～9 cm深度出苗率最高,在壤土中1～7 cm深度出苗率最高,超过11 cm不能出苗。 相似文献
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为研究沉水植物在不同水深和生长时期对不同种类入侵植物的响应,选取2种湿地入侵植物凤眼莲Eichhornia crassipes、水盾草Cabomba caroliniana和2种常见本地沉水植物黑藻Hydrillaverticillata、菹草Potamogeton crispus为研究对象,通过模拟试验探究在不同水深（0.2、0.4 m）和生长时期（生长初期和生长旺期）的本地沉水植物对2种入侵植物的响应。结果显示,当水深为0.4 m时更有利于黑藻的生长,并可削弱入侵植物对黑藻生长的消极作用,而水深对菹草的生长无显著影响;入侵植物种类对本地沉水植物的生长无显著影响,但影响方式却存在差异,其中水盾草倾向于直接抑制本地沉水植物的生长,而凤眼莲可以通过降低水体透明度以及总磷含量进而间接抑制本地沉水植物的生长。此外,外来植物在本地沉水植物生长初期入侵对本地沉水植物产生的消极影响较生长旺期入侵时更显著。表明凤眼莲及水盾草入侵对本地沉水植物生长的影响机制存在差异,本地沉水植物在适宜水深和生长旺期对2种入侵植物具有更强的抵抗能力。 相似文献
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外来杂草假臭草的特征特性 总被引：5，自引：1，他引：4
假臭草为菊科泽兰属一年生草本植物,原产南美,现散布于东半球热带地区.假臭草于20世纪80年代传人我国,在香港、福建厦门、广东南部、澳门、海南和台湾均有分布.假臭草繁殖速度快,对土壤肥力吸收能力强,能释放化感物质抑制其他植物生长,对入侵地农林业生产与生物多样性带来极大的危害.本文在调查研究及查阅大量文献的基础上,归纳了外来杂草假臭草的形态特征、生活史、起源、入侵途径、生境类型、营养和环境条件、在我国的分布、可能扩散的区域、经济和生态影响、预防控制和管理措施等. 相似文献
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近年来春季麦田草害调查时,发现草害重的田小麦纹枯病也较重。1983～1984两年的调查结果,重草田内重病田比例大:总草复盖度>40％的三级草害田10块内,发病率>50％的重病田块占80％;总草复盖度20～40％的二级草害田37块内,重病田占64.7％;总草复盖度<20％的一级草害田内,重病田占47.7％。这主要因为杂草增加 相似文献
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We conducted a glasshouse study to examine effects of hydrology on the growth and physiology of Lygodium microphyllum (Old World climbing fern), an invasive exotic that is rapidly colonising forested wetlands in Florida, USA. We assessed the fern's growth and physiological responses to three hydrological treatments – flood, drought and field capacity. To further explore the physiology of the treatment responses of L. microphyllum , we also sprayed each plant with gibberellic acid, paclobutrazol (gibberellin inhibitor) or a water control solution (at a rate of 5 mL three times per week) using a 3 × 3 factorial design. Flooding reduced relative growth rate by 55%, whereas periodic exposure of ferns to a soil water potential of −1 MPa did not affect growth or physiology. Flooding led to substantial decreases in specific leaf area and area-based rates of pinna photosynthesis, resulting in a 64% lower rate of photosynthesis per unit pinna mass. Application of growth regulators had no effect on fern growth, morphology or physiology. Even though flooding substantially reduced growth, L. microphyllum still showed a positive relative growth rate after >2 months of inundated soils. This apparent hydrological plasticity is likely a contributing factor to the introduced fern's widespread establishment across a range of plant communities within the Florida Everglades ecosystem. Short-term manipulation of site hydrology does not appear to be an effective management option. Consequently, this has considerable implications for the Everglades, which is undergoing a 30-year system-wide hydrological restoration. 相似文献
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以2010年TM影像为数据源,应用ArcGIS、Erdas软件对影像解译,把关中-天水经济区的土地利用景观分为6大景观类型。运用景观格局分析软件Fragstats 3.3,选择景观类型所占景观面积的比例、斑块个数、最大斑块指数、形状指数、平均分维数、连接度指数,从景观类型级别上探讨了景观格局指数的粒度效应,并对部分景观指数随粒度变化曲线进行了拟合。结果表明：在粒度为30～600 m,各景观类型的不同景观格局指数呈现出4种变化趋势: ① 指数值基本不变;② 指数值呈现有规律的上升或下降,有明显拐点;③ 指数值呈现有规律的上升或下降,但是拐点不明显;④ 指数无规律变化;部分景观指数随粒度变化曲线,可分别用三次函数和线性函数进行拟合;关中-天水经济区各景观类型景观指数计算的适宜粒度范围是耕地为120 m、林地为120～160 m、草地为90～130 m、水域为90～110 m、建设用地为90～130 m、未利用地为110～160 m。 相似文献
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The harvester ant Messor barbarus can be responsible for high weed seed losses in dry land cereals in Spain. Because weeds occur in patches, harvester ants have to be able to find and exploit patches. However, seed patches can differ in size and may, therefore, differ in the probability of being discovered and exploited. Here, 90 patches varying in size from 0.25 to 9 m2 were created in three 50 × 50 m subareas in a cereal field. Oat seeds were sown as weed seed surrogates in the patches at 2000 seeds m?2. After 24 h, those remaining were collected and the exploitation rate (the percentage of seeds removed per patch discovered by ants) was estimated. Harvester ant nests and the location of the seed patches were georeferenced and used to estimate distances between them. The patch encounter rate (the proportion of patches discovered by the ants) decreased slightly, but significantly, with decreasing patch size, though not the exploitation rate, which was lowest in the smallest patches (78–94%) and highest in the largest (99–100%). Seed patches that were not found or partially exploited were mostly located in subareas with a lower ant nest density or a longer distance away from the nearest nest than seed patches that were fully exploited. The results of this study indicate that the interaction between the spatial distribution of ant nests and the patchy distribution of seeds can create opportunities for seeds to be subjected to lower levels of predation. 相似文献
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本文报道了新疆天山的１０种苔藓植物新记录：１．小叶管口苔Ｓｏｌｅｎｏｓｔｏｍａ ｍｉｃｒｏｐｈｙｌｌｕｍ，２．短托柄花萼苔Ａｓｔｅｒｅｌｌａ ｙｏｓｈｉｍｎａｇａｎａ，３．大孢对叶藓Ｄｉｓｔｉｃｈｉｕｍ ｍａｃｒｏｐｏｒｕｍ。４．旱藓Ｉｎｄｕｓｉｅｌｌａ ｔｈｉａｎｓｃｈａｎｉｃａ。５．缨齿藓Ｊａｆｆｕｅｌｉｂｒｙｕｍ ｗｒｉｇｈｔｉｉ。６．钝叶紫萼藓Ｇｒｉｍｍｉａ ｏｂｔｕｓｉｆｏｌｉａ．７．陈 相似文献
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拟中华半轮线虫新种(Hemicriconemoides parasinensis sp. nov.)模式标本采集于辽宁省沈阳市沈阳农业大学校园的丁香(Syringa oblata)根际土中,在河南省安阳市安阳公园的小叶女贞(Ligustrum quihoui)根际土中也有分布。主要鉴别特征是虫体头区圆形,头环2个,第1头环略小于或等于第2头环,排泄孔位于肠的前端(Rex=29~33),体长中等,口针中等(76~86 μ m),体环数R值中等(96~110),卵巢单生前伸,受精囊长圆形,尾部宽圆锥形、尾端半球形圆;幼虫具指状的棘片,约12~16排,后翻;雄虫未见。该新种虫体形态特征与中国半轮线虫(H. sinensis Vovlas,1988),芒果半轮线虫(H. mangiferae Siddiqi,1961)和微小半轮线虫(H. minutus Esser,1960)相近似。 相似文献
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The economic benefits of using site‐specific weed management (SSWM) are related to the proportion of the field that is weed‐infested, the number of weed patches and the spatial resolution of sampling and spraying technologies. In this paper we simulate different combinations of these factors using parameter values obtained for Avena sterilis ssp. ludoviciana growing in Spanish winter barley crops. The profitability of SSWM systems increased as the proportion of the field infested by this weed decreased and when patch distribution was more concentrated. Under most of the conditions tested, positive net returns for SSWM were obtained when the weed‐infested area was smaller than 30%. The highest net return occurred using a 12 m × 12 m mapping and spraying resolution. The critical parameter that determined the economic viability of patch mapping and spraying resolution was the technology costs. The site specific strategy was economically superior to the standard strategy (overall herbicide application) in most cases. However, the differential between the two strategies decreased when the number of patches and the resolution of mapping and spraying increased, such that the highest net returns were obtained with a single patch covering 14% of the field and using a 12‐m mapping and spraying resolution; whereas the worst net returns were obtained for all patch numbers when 64% of the field was infested and a 3‐m mapping and spraying resolution was used. 相似文献
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Spread of proso millet (Panicum miliaceum L.) in Ontario, Canada. II. Dispersal by combines 总被引：1，自引：0，他引：1
Seeds of proso millet (Panicum miliaceum L.) are moved between and within fields on combine harvesters. The dispersal of seeds of two biotypes of P. miliaceum by combine harvesters was quantified. The golden-seeded biotype of this weedy annual grass was known to have larger seeds and to experience less seed shattering than the black-seeded biotype. An average of 3·3% of the seeds on the plants of the black-seeded biotype was carried more than 50 m by combines, while 0·9% of the golden seeds were carried the same distance. The densities of the seed rain within 50 m of the weedy patches were 3·7 seeds m−2 for the black-seeded biotype and 9·7 seeds m−2 for the golden-seeded biotype. This difference was proportional to the difference in the number of seeds in the respective source patches. The numbers of seeds deposited at various points within 50 m of source patches were close to uniform for both biotypes. There was, however, a significant difference (P < 0·05) in the distributions of the seeds of the two biotypes. 相似文献
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乌兰布和沙漠天然灌丛防风阻沙效益研究 总被引：3，自引：0，他引：3
对乌兰布和沙漠封沙育草带内的天然灌丛周围风速及输沙量的野外观测结果表明,天然白刺灌丛沙堆对风沙流具有阻滞作用,风沙流在迎风面受阻堆积,在背风面风速下降40.3~42.1%,并形成低速区,引起沙粒堆积;沙蒿灌丛对2m高处风速没有影响,但可引起灌丛背风面近地表0.5m处风速下降20.5%。灌丛的迎风面存在一个减速区,灌丛顶部及两侧为加速区,灌丛背风面存在一个静风区和一个尾流区。灌丛侧面的输沙量最大,背风面输沙量最小,迎风面2H处输沙量大于1H处,这与各点的风速变化是一致的。对不同盖度沙地的输沙量进行的观测表明,输沙能力随植被盖度的增加而减小,流动沙地输沙量最大,在5.6~9.4m/s风速范围内输沙量为2.25~21.75g,半固定沙地的输沙量次之,为0.32~13.58g,固定沙地最小,为0.06~2.29g。 相似文献
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ChengChen PAN 《干旱区科学》2012,4(1):19-28
Pollen limitation of plant reproduction occurs across Angiosperms,particularly those in patched habitats.We investigated the relationship between pollen limitation and patch variables (patch size,visitation frequency) in the desert plant Hedysarum scoparium (Fabaceae),which is an important xerophyte in the arid and semi-arid regions of Northwest China and can grow well as a pioneer plant in shifting sand dunes.We observed insect visitation to H.scoparium over two flowering seasons and estimated pollen limitation using fruit set and seed production.Our results indicate that fruit set and seed production increased significantly with pollen supplementation compared with open pollination.Hedysarum scoparium was pollinated by over 8 species of bees,with 88.4% of visits made by introduced honeybees (Apis mellifera).Bee visitation varied significantly among the patches of habitats,but not associated with patch size of habitat.In general,pollen limitation occurred more strongly during fruit set than during seed production.The patches that received higher rates of pollinator visits were less pollen limited for fruit set.Pollen limitation for seed production,however,was not associated with pollinator visitation frequency.We conclude that pollen limitation in H.scoparium was caused by more than one reason,not just pollinator visits. 相似文献
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If weeds occur in aggregated spatial patterns, it is possible to reduce herbicide use by spraying only weed patches. The reduction in herbicide use will then depend on the spatial resolution of the patch sprayer and the weed-free area at that level of resolution. Three distance measures are presented that describe the weed spatial pattern at different levels of resolution. They give information on aspects of pattern that are relevant to patch spraying. The distance measures were applied to a spatial pattern of Galium aparine L. seedlings recorded in an area of 18.0 m × 32.4 m. In this area, the herbicide use of an idealized patch sprayer that detects and sprays all weeds with a spatial resolution of 1.0 m would be 41% of the amount required for a whole-field application. Spraying with a finer spatial resolution of 0.5 m would give a further 26% reduction in herbicide use. 相似文献